1. Field of the Invention
The invention relates to a hydrophobicizing additives, a process for producing them, and to their use.
2. Description of the Related Art
Polymers based on vinyl esters, vinyl chloride, (meth)acrylate monomers, styrene, butadiene and ethylene are used, in particular in the form of their water-redispersible polymer powders, in many applications, for example as coating agents or adhesives for a wide variety of substrates. Redispersion powders are also used as binders in hydraulically setting coatings or adhesives such as mortar for thermal insulation, tile adhesives, and renders or jointing compositions based on cements or plaster of Paris. In the case of lime- or cement-bound building materials such as renders, knifing fillers, jointing compositions and building adhesives, protection against weathering influences, for example, rain or snow, is frequently required. It is therefore necessary to hydrophobicize the building materials.
In the prior art, redispersion powders which are used for improving mechanical strength have been modified by means of small proportions of hydrophobicizing agents. EP 493168 A1 describes hydrophobically modified redispersion powders based on water-insoluble, film-forming polymers which contain from 0.5 to 20% by weight of silicones as hydrophobic component. WO 2004/080909 A2 describes redispersion powders which contain polyalkylalkylsiloxanes having long-chain hydrocarbon radicals in an amount of from 0.1 to 20% by weight, based on the organic polymer fraction, for hydrophobicization. EP 1193287 A2 describes the use of redispersion powder compositions which contain from 0.1 to 30% by weight of carboxylic esters as hydrophobicizing component in addition to a proportion of water-insoluble, film-forming polymers. EP 1394193 A1 describes an analogous redispersion powder comprising carboxylic esters which contain glycerol, diglycerol or triglycerol as an alcohol component. EP 0741759 B1 and EP 0741760 B1 describe dispersion powder compositions based on water-insoluble, film-forming organic polymers with a proportion of silicon compound of from 0.1 to 30% by weight, based on the organic polymer fraction. In all these starting points for a solution to weathering problems, redispersion powders based on film-forming polymers which are used primarily for improving the mechanical strength of building material compositions are admixed with a small proportion of hydrophobicizing agent. The ratio of silicon compound to film-forming polymer is limited. Thus, the degree of hydrophobicization cannot be set independently, since the amount of redispersion powder used depends on the desired mechanical strengths of the building materials to be modified and thus primarily on the proportion of polymer in the powder.
For pure hydrophobicization, including that of building materials, use is made of redispersible hydrophobicizing agents which are composed of a hydrophobicizing component and a protective colloid which ensures redispersibility. EP 279373 B1 and EP 508155 B1 describe hydrophobicizing agents which comprise organopolysiloxane and protective colloid and are obtained by drying of the siloxane component in the presence of a water-soluble polymer (protective colloid). DE 10323205 A describes a hydrophobic additive comprising protective colloid and fatty acid (derivative), with the fatty acid or the fatty acid derivative being dried in the presence of from 30 to 95% by weight of protective colloid. DE-A 19542443 recommends using a combination of redispersion powder and redispersible organosilicon compound. A disadvantage of the use of hydrophobicizing agents stabilized by means of protective colloid is that a high proportion of protective colloid has to be used in order to make the hydrophobicizing agent redispersible. However, this protective colloid is water-soluble, contributes nothing to the setting of the building materials and tends to wash out on intensive contact with water.